Intervertebral disc as a source of pain

Abstract

Back pain, although not usually life threatening, is a major public health problem both here in the UK and in Western societies in general. It affects a large number of people each year and is a cause of considerable economic loss and personal suffering. Point prevalence rates indicate that it affects between 12% and 35% of the population, of whom 20% will seek medical attention. One study in the UK estimated that in 1998, direct health-care costs associated with back pain were approximately £1.6 billion, but the total costs related to lost productivity closer to £11 billion. 2 A number of anatomical structures within the back may be responsible for back pain; intervertebral discs, facet joints, muscles, ligaments, and nerve root sheaths are all possible ‘pain generators’. Of these, the intervertebral discs, facet joints, and sacroiliac joints are implicated in up to 45, 40, and 13% of the cases, respectively. Furthermore, more than one structure may be contributing to the pain at any one time. The intervertebral disc may produce pain either as a result of intrinsic degeneration (discogenic pain) or by extrinsic compression of neural structures in the spinal canal, producing radicular pain. Disc degeneration also results in loss of disc height which, in turn, may alter the mechanics of the axial skeleton. These changes may produce pain in other structures including the zygapophyseal (facet) joints and may ultimately result in spinal stenosis. Discogenic pain is defined as axial pain originating in a degenerative disc. Radicular pain is the pain radiating in the distribution of a spinal nerve caused by the irritation of the sensory root or dorsal root ganglion (DRG) of that spinal nerve.Although degenerative disc disease (DDD) is the most common cause of such compression, there are other pathologies which may produce radicular pain.